 /*******************************************************************************
  * Copyright (c) 2003, 2005 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.commands;

 import java.util.Map ;

 /**
  * A handler is the pluggable piece of a command that handles execution. Each
  * command can have zero or more handlers associated with it (in general), of
  * which only one will be active at any given moment in time. When the command
  * is asked to execute, it will simply pass that request on to its active
  * handler, if any.
  * <p>
  * This interface is not intended to be extended by clients.
  * </p>
  *
  * @since 3.0
  * @deprecated Please use the "org.eclipse.core.commands" plug-in instead.
  * @see org.eclipse.core.commands.IHandler
  */
 public interface IHandler {

     /**
      * Registers an instance of <code>IHandlerListener</code> to listen for
      * changes to properties of this instance.
      *
      * @param handlerListener
      * the instance to register. Must not be <code>null</code>. If
      * an attempt is made to register an instance which is already
      * registered with this instance, no operation is performed.
      */
     void addHandlerListener(IHandlerListener handlerListener);

     /**
      * Disposes of this handler. This method is run once when the object is no
      * longer referenced. This can be used as an opportunity to unhook listeners
      * from other objects.
      */
     public void dispose();

     /**
      * Executes with the map of parameter values by name.
      *
      * @param parameterValuesByName
      * the map of parameter values by name. Reserved for future use,
      * must be <code>null</code>.
      * @return the result of the execution. Reserved for future use, must be
      * <code>null</code>.
      * @throws ExecutionException
      * if an exception occurred during execution.
      */
     Object execute(Map parameterValuesByName) throws ExecutionException;

     /**
      * Returns the map of attribute values by name.
      * <p>
      * Notification is sent to all registered listeners if this property
      * changes.
      * </p>
      *
      * @return the map of attribute values by name. This map may be empty, but
      * is guaranteed not to be <code>null</code>. If this map is not
      * empty, its collection of keys is guaranteed to only contain
      * instances of <code>String</code>.
      */
     Map getAttributeValuesByName();

     /**
      * Unregisters an instance of <code>IPropertyListener</code> listening for
      * changes to properties of this instance.
      *
      * @param handlerListener
      * the instance to unregister. Must not be <code>null</code>.
      * If an attempt is made to unregister an instance which is not
      * already registered with this instance, no operation is
      * performed.
      */
     void removeHandlerListener(IHandlerListener handlerListener);
 }

